Signal receiving and transmitting apparatus



. 1949 H. w. BECKER 2,491,244

SIGNAL RECEIVING AND TRANSMITTING APPARATUS Filed April 27; 1946 2Shets-Sheet 1 Dec. 13, 1949 H. WJBECKER 2,491,244

' SIGNAL RECEIVING AND TRANSMITTING APPARATUS Filed April 27, 1946 2Sheets-Sheet 2 u l :7 E

2 m; a r

- my r29 Patented Dec. 13, 1949 UNITED STATES PATIENT OFFICE SIGNALRECEIVING AND TRANSMITHNG APPARATUS 18 Claims.

This invention relates to signal receiving and transmitting apparatusand more particularly to the receiving of signals from and transmissionof signals to a remote point without the use of a local power supply.

In my Patent No. 2,389,949 there is described and claimed an apparatusfor receiving power and signals from a remote point over a single pathsuch as a pair of wires. The present invention provides an improvementin the apparatus of the patent to permit generation and transmission aswell as reception of signals.

One of the objects of the invention is to provide apparatus in which atuned circuit may be used to select a signal to be received or toproduce oscillations for transmission.

Another object is to provide apparatus which may be supplied with powerfrom a remote point to produce signal oscillations for transmission tothe remote point.

Still another object is to provide apparatus which can easily andquickly be switched to act as either a receiver or transmitter.

The above and other objects and advantages of the invention will be morereadily apparent from the following description when read in connectionwith the accompanying drawing, in

which- Figure 1 is a circuit diagram of one form of apparatus embodyingthe invention; and

Figures 2 and 3 are circuit diagrams of'al'ternative constructions.

The apparatus of Figure l is substantially identical with that of myPatent No. 2,389,949 with the exception that switches and other circuitcomponents have been added to enable it to function as both a receiverand a transmitter. As shown the apparatus is adapted to receive anyselected one of five signals transmitted over a supply circuit formed bya pair of wires I and II which may connect terminals on the apparatus toa remote point. The apparatus may also generate signals at any one offive selected frequencies which may be transmitted over the circuitIll-II to the remote point. As described herein, the signals may beaudible signals such as voice or music, although it will be apparentthat any other desired type of signals could be received or transmitted.The wires Ill-I I are connected to a source of heating current and .to a

source of direct current, the heating current being at a supersonicfrequency in case the signals are in the audible range. When theapparatus is to be used as a receiver, the wires In and Il may alsosupply five carrier currents of different frequency modulated by theaudible signal frequencies, the carrier currents bein in each case at afrequency diflferen't than that of the heating current.

The apparatus comprises an electron discharge tube shown as a tetrodehaving a filament type cathode I2, a control grid I3, a screen grid I4and a plate I5. The supply line IIJ is connected through a .resonantcircuit including a coil I6 in series with a second coil I! which is inparallel with a condenser I8. The condenser I8 and the coil H areconnected through a line I9 and a bypass condenser 2| to the line II.The resonant circuit I6--I8 is tuned to offer a minimum impedance to theheating current but substantially to block the carrier frequencies.

The coil I'I serves as the primary of a transformer whose secondary 22is connected across the filament I2. The transformer blocks the directcurrent so that the filament is directly heated by the high frequencyheating current.

The plate I5 of the tube is connected through a plate load resistor 23to the line I9. The direct voltage in the supply circuit will thereforebe impressed on the plate across the load resistor, the alternatingcurrents being bypassed back to the supply 'line'through the condenser2| The screen grid |4is also connected to the line I9 through a droppingresistor 24 and is bypassed to the'sllpply line through a condenser 25to eliminate any alternatin components.

The output signal is reproduced through a speaker or headset 26 which isconnected to the supply line II and which may be connected to the platel5 through a blocking condenser 21. While the signal reproducing devicehas been shown as a headset for reproducing audible signals, it will beunderstood that it could be any other desired type of signal reproducerand that it could be connected to the tube through one or more amplifierstages, if desired.

The signal currents are conducted from the.

wire II! through a blocking condenser 28 to eliminate direct current toa coil 29 which is grounded at 30., Since the wire II is grounded asillustrated at 3|, the coil 29 is connected across the supply line. Thecoil 29 may be tuned to resonance with any one of the several carriervfrequencies by connectin in parallel therewith one of five condensers32. For this purpose the condensers are connected to separate contactswhich may be selectively engaged by a switch .arm 33 connected .to oneside of the coil .29. The other sides of the condensers may be grounded.at 3.4. The condensers may be adjusted to tune the circuit to theselected frequency so that any one of the five carrier frequenciessup-plied over the wires I t and I I may be selected for reproduction.In will be understood that if desired a single variable condenser couldbe employed to tune the circuit to any selected frequency within theoperating range of the apparatus. The coil 29 is connected to thecontrol grid I3 of the tube through a coil 35 which is loosely coupledto the coil 29. The coil 35 is connected at one end to the grid l3 andat its other end to the filament I2 through a grid bias resistor 36bypassed by a condenser 31. The coil 35 may also be tuned to any one ofthe signal carrier frequencies by connecting in parallel therewith anyselected one of five condensers 36 by means of a switch arm 39.Preferably the arms 33 and 39 are connected together so that both coils29 and 35 will always be tuned to the same frequency.

To use the apparatus for receiving signals sent out over the wires Ii!and H, the parts may be connected as shown in Figure 1. In thiscondition the wire It] is connected through a switch 4| to the condenser28, and the plate 55 of the tube is connected through a switch 42 to thecondenser 21 and resistor 23. At this time the apparatus issubstantially identical to that described in my Patent No. 2,389,949 andoperates in the same manner.

To use the apparatus for transmitting signals back over the wires Iiiand H, the line It may be connected through the switch to the lower endof coil 29 through an inductance 43 and a condenser 44, the inductance43 being provided to match the impedance of the line duringtransmission. The plate I5 of the tube may be connected through theswitch 42 to a wire 45 connected through a condenser 46 to the upper endof coil 29. The wire 45 may also be connected through a switch 41 and anR. F. choke 48 to the line Hi. There is also provided for transmittin asignal translating device shown as a microphone 49 which is connectedthrough a switch 5I across the grid bias resistor 36. The severalswitches 4!, 42, t! and BI may be interconnected for simultaneousoperation.

In transmitting the switches are all moved to their positions as shownin dotted lines. At this time the heating current and direct current tosupply plate voltage are supplied by the wires Ill and I I, but nosignal currents are supplied. The filament I2 will be heated in the samemanner as that described above, the choke 48 serving to keep the highfrequency signal current out of the remainder of the circuit. The platecurrent of the tube flows through the wire 45 and condenser 46 to thecoil 29 which may be tuned by one of the condensers 32 to any desiredfrequency. This arrangement causes the tube to oscillate at the selectedfrequency, the oscillations being fed back to the grid through the coil35. The grid supply voltage may be modulated by impressin an audible orother desired signal on the translating device 49 to modulate theoscillations. The modulated oscillations will be fed back to the circuitI UI I through the condenser 44 and inductance 43 and may be picked upfor reproduction at the remote point or at any other point supplied bythe circuit I l.il I. It will be understood that this circuit may beeither a wired or a wireless circuit, as desired.

Figure 2 illustrates an alternative arrangement which diiiers fromFigure 1 principally in that it provides more power for bothreproduction and transmission of signals. As shown in this figure,

supersonic heating current and direct current may be supplied over acircuit including a pair of wires 52 and 53. The wire 52 is connectedthrough a tuned circuit including coils 5 and 55 and a condenser 56 inparallel with the coil 55 to the wire 53 through a resistor 57 and abypass condenser 58 to ground at 59, the wire 53 being grounded at 5|.The winding 55 serves as the primary of a transformer whose secondarywinding 62 is connected to the filaments 63 and B4 of a pair of electrondischarge tubes 65 and 66. The wire 52 is also connected through a loadresistor 61 to the plate 68 of the tube 65.

The tube 65, as shown, is a double tube including a diode section and atetrode section such, for example, as a 185. The diode sectioncoroprises a plate 69, and the tot-rode section includes in addition tothe plate 58 a control grid '4! and a screen grid The tube isillustrated as a p-entode s 11-935 and includes a plate 13, a controlgrid 34, a screen grid and a suppresser grid 35.

To utilize the circuit for transmitting, which is the condition shown infull lines in Figure 2, the tube 68 serves as an oscillator whoseoscillations may be modulated through the tube 55. As shown, the plateis of the tube 35 is connected through a winding Tc having variablecondenser 18 in parallel therewith to the line 52. The winding i? mayserve as the primary of a transformer whose secondary I9 is connectedthrough a condenser BI across the lines 5253 to transmit 0scillationsthereto. The condenser it may be a single variable condenser, as shown,or may comprise a bank of condensers such as those shown at 32 or 38 inFigure 1 to vary the tunin of the circuit. The screen grid 75 isconnected through an R. F. coil 82 to the lower ends of the coil I? andcondenser I8 and may be connected through a switch 83 and a condenser 84to the upper end of a coil 85 which is loosely coupled to a coil 86. Thecoils 85 and 36 may be tuned by a variable condenser 81 connected inparallel therewith by a switch 88, as shown. For transmitting the lowerend of the coil 85 is connected through a switch 89 to the cathode 5%,and the upper end is connected through a condenser and a switch 92 tothe control grid 4, a "bypass resistor 93 preferably being provided.With the circuit arranged and the switches in the position shown, thetube 66 will oscillate at a frequency determined by adjustment of thecondensers it and 8?, and the oscillations will be transmitted to theline through the transformer I9.

To modulate the oscillations a signal translating device such as amicrophone 94 is provided connected through a condenser 95 and a switch96 to the grid H of the tube 65. Preferably a bypass resistor 97 isprovided across the grid circuit. The plate 68 of the tube 55 isconnected through a condenser 98 and a switch 99 to the suppresser grid15 of the tube 66 to modulate the oscillations. Preferably, a bypassresistor I0! is connected across the suppresser grid circuit, as shown.With this construction when a signal is impressed on the microphone 94the signal will be amplified in the tube 65 and impressed on thesuppresser grid 16 of the tube 63 to modulate the oscillations producedby the tube 56. The modulated oscillations are impressed on the line5253 and may be reproduced at any desired remote point.

To use the apparatus for receiving signals the several switches arethrown to the positions op- 75 posite to those shown. An additionalswitch I02 is-moved simultaneously to connect a condenser I03'acrossthe. coil 86. The switch 99 connects ar-signal reproducing. device such.as a headset I04 to the :plate 68 of the tube 65.. The switch 96connects the control. grid II of the tube 65 to a wiper on a.potentiometer I05 which is bypassed by-a condenser I66 and the upper endof which is connected to the plate 69 for the diode section of the tube65. The plate 69 is also connected through a wire I01 and the switch 92to the upper end of the coil 86.

At this time the tube 66 is inactive and the double tube 65 serves bothto detect and to amplify the signal supplied over the wires 52 and 53.For this purpose the wire 52 is connected througha wire I68 and theswitch 83 to the tuned circuit provided by the condenser 81, the coils85 and 86 and the condenser I03. The signal. current passed. by thetuned circuit is connected through the wire I61 to the plate 69 of thetube 65. The current flowing in. the diode section of the tube 65 may beconducted through the variable resistor I65 which serves as a volumecontrol to the control grid II of the tetrode section of this tube. Thesignal detected is amplified in the tetrode section of the tube and isreproduced. by the headset I04.

In the receiving position, the particular type of tuned circuit formedby the coils 85 and 86 and the condensers 8'! and. I03 enablessubstantially any desired voltage to be provided at the plate 69 andfurther enables this voltage to be maintained substantially constantthroughout the full range. The incoming signal finds one path to groundthrough condenser 81 and a second through. coils 85 and 85 and condenserI93 in series. If coil 86 and condenser I93 are tuned exactly toresonance with the signal they appear as a series resonant circuitoffering zero impedance between coil 85 and ground. The voltage appliedto plate 69 is equal to the drop across the condenser I03 which is equalto and out of. phase with the drop across the coil 86.

If more voltage is desired at the plate 69 the condensers 81 and I03 maybe adjusted to increase the capacity of 81 and reduce the capacity ofI03. This makes the combination 8I--85 capacitative and the combination86I63' inducti've to maintain the overall tuning the same. However, thevoltage drop across I93 is increased. By proper design of the elementsthe voltage may be made to increase or decrease at selected frequenciesto compensate for varying line attenuation or the like andmaintain thevoltage constant at the plate 69 at all frequencies. It will be seenthat a circuit of this type would be highly advantageous in theapparatus illustrated as well as in many other types of apparatus.

Figure 3 illustrates still another construction in which the necessityfor switching between receiving and transmitting operations iseliminated. The circuit elements as shown in Figure 3 are substantiallysimilar to those of Figure 2 and function in general in the same manner.The leads which connect to terminals on the apparatus are shown at III)and III and supply heating current at supersonic frequency, at least onesignal carrier current modulated at an audible frequency and a directcurrent whose polarity is as indicated. The receiving part of theapparatus includes a tube H2 similar to the tube 65 of Figure 2 having afilament H3, a plate II4, grids H5 and IIS and a plate 1. The filamentH3 is connected to a transformer secondary winding I18 which ismagnetically coupled to a winding; I I9 having a condenser I 2|; inparallel therewith and connected through a. coil I22 to the wire II I.The coils and; condenser form a circuit tuned to: the heating currentfrequency and substantially block the signal frequency so that thefilament will be heated by the supersonic frequency only. The wire IIIalso connects througha. blocking condenser I23 to a tuned cir cuitincluding condensers I24 and coils I25 to the plate H4. The. plate isconnected through a resistance I26 to the filament and a wiper I21engages the resistance -I26 to supply a signal voltage throughacondenser I28 to the grid II5.

In this way the signal voltage is impressed on the:

tube II 2 which serves to amplify the. signal. The plate II-"I isconnected as shown to a signal reproducing device such. as earphones I29to reproduce the. signal, the other parts of the circuit beingsubstantially identical with the circuit elements at the right of Figure2 This portion of the circuit serves to receive and re.- produce thetransmitting signals without requiring a local power supply.

The transmitting portion of the circuit includes a tube Ir3 I similar tothe tube 66 of Figure 2 and having a. filament I32, a control grid I33,a screen grid I34, a suppressor grid. I and a plate I36. The filamentI32 is heated by the supersonic heating current through a. transformersecondary Winding I31 connected to the wire III through tuning elementsincluding coils I38 and I39 and condenser MI. The control grid I33 isconnected through a tuned circuit shown as including a crystal I42 tothe screen grid I34. With this. connection the filament control grid andscreen grid act as a triode and the crystal I42 causes the tube tooscillate. Preferably the crystal is tuned to a frequency difiering fromboth the heating current frequency and the signal frequency. A signaltranslating device such as a microphone I43 is connected to thesuppressor grid I35 to modulate the oscillations. The plate is connectedthrough a circuit including a coil I44 and a condenser I45 tuned to theoscillating frequency to the wire III as shown. A secondary winding I46coupled to the winding I44 connects through condensers M1 to the wiresIll] and I. II to impress the modulated oscillations thereon.

With this construction when a signal current is applied to the wires II6 and III at the frequency to which the tuned circuit I24I2-5 isresonant, the signals will be reproduced through the tube H2 at theearphones I29. The signal current will not 'afiect the transmittingparts of the circuit since it is blocked by the tuned circuit. I'M-I45.When it is desired to transmit a signal such as an audiblesignal it maybe impressed on the microphone I43 to modulate the oscillations producedby the tube I3I. The modulated oscillations can be transmitted by thewires III) and III to a desired point of reception.

While several embodiments of the invention have been shown and describedin detail, it is to be understood that they are illustrative only andare not to be taken as a definition of the scope of the invention,reference being had for this purpose to the appended claims.

What is claimed is:

1. A. signal receiving and transmitting apparatus comprising an electrondischarge tube having a cathode, a grid and a plate, terminals connectedto the cathode to supply alternating heating current of supersonicfrequency thereto, the terminals also being adapted to supply a signalvoltage of a'different frequency than the heating current, a microphone,means including a switch selectively to connect the grid of the tube tothe terminals or to the microphone, a signal reproducing device, andmeans including a switch solectively to connect the plate of the tube tothe reproducing device to reproduce a signal supplied at the terminalsor to the terminals to supply a signal thereto.

2. A signal receiving and transmitting apparatus comprising an electrondischarge tube having a cathode, a grid and a plate, terminals connectedto the cathode to supply alternating heating current of supersonicfrequency thereto, the terminals also being adapted to supply a signalvoltage of a different frequency than the heating current, a tunedcircuit, a microphone, means including a switch selectively to connectthe grid of the tube through the tuned circuit to the terminal toreceive the signal or to the microphone for transmitting, a signalreproducing device, and means including a switch selectively to connectthe plate of the tube to the signal reproducing device or through thetuned circuit to the grid of the tube to cause the tube to oscillate.

3. A signal receiving and transmitting apparatus comprising an electrondischarge tube having a cathode, a grid and a plate, terminals connectedto the cathode to supply alternating heating current of supersonicfrequency thereto, the terminals also being adapted to supply a signalvoltage of a different frequency than the heating current, a tunedcircuit resonant to the signal frequenc and anti-resonant to the heatingcurrent frequency, means including a switch to connect the terminalsthrough the tuned circuit to the grid of the tube to cause it to respondto the signal voltage, means including a switch to connect the plate ofthe tube through the tuned circuit to the grid of the tube to cause thetube to oscillate, a signal reproducing device, means includin a switchto connect said device to the plate of the tube to reproduce thesignals, a microphone, and means including a switch to connect themicrophone to the tube to modulate the oscillations thereof.

4. A signal receiving and transmitting apparatus comprising an electrondischarge tube having a control circuit and an output circuit, afilament in the tube to supply power thereto, terminals adapted to beconnected to a source of alternating heating current, means connectingthe filament to the terminals to be heated by the heating current, atuned circuit, a signal translating device, a signal reproducing device,and switch means to connect the terminals through the tuned circuit tothe control circuit and the signal reproducin device in the outputcircuit in one position and in another position to'connect the outputcircuit through the tuned circuit to the control circuit to cause thetube to oscillate, to connect the translating device to the controlcircuit to modulate the oscillations, and to connect the output circuitto the terminals to impress the modulated oscillations thereon.

5. A signal receiving and transmitting apparatus comprising an electrondischarge tube having a control circuit and an output circuit, afilament in the tube to supply power thereto, terminals adapted to beconnected to a source of alternating heating current, the terminalsbeing adapted to supply signal current at a frequency different thanthat of the heating current, means including a circuit resonant at theheating current frequency and anti-resonant at the signal means toconnect the terminals through the tuned circuit to the control circuitand the signal reproducing device in the output circuit in one positionand in another position to connect the output circuit through the tunedcircuit to the control circuit to cause the tube to oscillate, toconnect the translating device to the control circuit to modulate theoscillations, and to connect the output circuit to the terminals toimpress the modulated oscillations thereon.

6. A signal transmitting apparatus comprising an electron discharge tubehaving an input circuit and an output circuit, a filament in the tube,terminals adapted to be connected to a source of alternating heatingcurrent, means connecting the terminals to the filament to supplyheating current thereto, resonant means connecting the input and outputcircuits of the tube to cause the tube to oscillate at a frequencydifferent than that of the heating current, a signal translating deviceconnected to the tube to modulate the oscillations, and means connectingthe output circuit of the tube to the terminals to impress the modulatedoscillations thereon.

7. A signal transmitting apparatus comprising an electron discharge tubehaving an input circuit and an output circuit, a filament in the tube,terminals adapted to be connected to a source of alternating heatingcurrent, resonant means connecting the input and output circuits of thetube to cause the tube to oscillate at a frequency different than thatof the heating current, means resonant at the heating current frequencyand anti-resonant at the oscillating frequency connecting the terminalsto the filament to supply heating current thereto, a signal translatingdevice connected to the tube to modulate the oscillations, and meansresonant at the oscillating frequency and anti-resonant at the heatingcurrent frequency connecting the output circuit of the tube to theterminals to impress the oscillations thereon.

8. A signal transmitting apparatus comprising an electron discharge tubehaving a filament, a plate and a plurality of grids, terminals adaptedto be connected to a source of alternating heating current, meansconnecting the terminals to the filament to supply heating currentthereto, resonant means interconnecting two of the grids to cause thetube to oscillate at a frequency different than that of the heatingfrequency, a signal translating device connected to a third grid tomodulate the oscillations, and means connecting the plate to theterminals to impress the oscillations thereon.

9. A signal receiving and transmitting apparatus comprising an electrondischarge tube having a filament, a plate and a grid, terminals adaptedto be connected to a source of alternating heating current, meansconnecting the terminals to the filament to supply heating currentthereto, the terminals also being adapted to supply a signal current ata frequency different than that of the heating current, a tuned circuitresonant at the signal current frequency, a signal reproducing device, asignal translating device, and switches having one position in whichthey connect the terminals through the tuned circuit to the grid of thetube and the signal reproducing device to the plate of the tube andanother position in which they connect the plate and grid through thetuned circuit to cause the tube to oscillate, the plate to the terminalsto impress the oscillations thereon and the signal translating device tothe grid to modulate the oscillations.

10. A signal receiving and transmitting apparatus comprising a firstelectron discharge tube having a filament, a plate and a grid, a secondelectron discharge tube having a filament, a plate and a plurality ofgrids, terminals adapted to be connected to a source of alternatingheating current, means connecting the terminals to the filaments of thetubes to supply heating current thereto, the terminals also beingadapted to supply a current at a frequency different than that of theheating current, a tuned circuit resonant at the signal currentfrequency, a signal reproducing device, a signal translating device, andmeans including switches having one position in which they connect theterminals to the grid of the first tube and the signal reproducingdevice to the plate of the first tube and a second position in whichthey connect two grids of the second tube through the tuned circuit, theplate of the second tube to the terminals, the grid of the first tube tothe signal translating device, and the plate of the first tube to a gridof the second tube.

11. A signal receivin and transmitting apparatus comprising a pair ofterminals adapted to be supplied with alternating heating current at onefrequency and with signal currents at difierent frequencies, electrondischarge means including filament, grid and plate elements, meansoffering a low impedance to the heating current and a high impedance tothe signal currents connecting the terminals to the filament elements,circuit means tunable to signal current frequency to connect theterminals to a grid element, a signal reproducin device to be connectedto a plate element to reproduce the signals, circuit means to connect toelements including at least one grid element to cause oscillations at afrequency different that the heating current frequency, a signaltranslating device to be connected to a grid element to modulate theoscillations, and circuit means to connect the plate element to theterminals to impress the modulated oscillations thereon.

12. A signal recieving and transmitting apparatus comprising a pair ofterminals adapted to be supplied with alternating heating current at onefrequency and with alternating signal current at a diiierent frequency,a pair of electron discharge tubes each including a filament, a grid anda plate, means offering a low impedance to the heating current and ahigh impedance to the signal current connecting the terminals to thefilaments to heat them, circuit means tunable to the signal currentfrequency to connect the terminals to a grid of one of the tubes, a sial reproducing device to be connected to the plate of said one of thetubes, circuit means tunable to a frequency to be connected to the othertube to cause it to oscillate, a signal translating device, means toconnect the translating device to a grid of the other tube to modulatethe oscillations, and means to connect the plate of the other tube tothe terminals.

13. The construction, defined in claim 12 in which the last named meanscomprises a tuned circuit tuned to the oscillating frequency.

14. A signal receiving and transmitting apparatus comprising a pair ofterminals adapted to be supplied with alternating heating current at onefrequency and with alternating signal current at a different frequency,a pair of electron discharge tubes each including a filament, a grid anda plate, means offering a low impedance to the heating current and ahigh impedance to the signal current connecting the terminals to thefilaments to heat them, a circuit tuned to the signal frequencyconnecting the terminals to a grid of one of the tubes, a signalreproducin device connected to the plate of said one of the tubes, acircuit tuned to a frequency different than the heating and signalfrequencies connected to the other tube to cause it to oscillate, asignal translating device connected to a grid of the other tube tomodulate the oscillations, and means connecting the plate of the othertube to the terminals to impress the modulated oscillations thereon.

15. The construction defined in claim 14 in which the last named meansis a tuned circuit tuned to the oscillating frequency.

16. In an electric signal handling apparatus, a tuned circuit acrosswhich a signal is impressed comprising two parallel branches, areactance 4 element in one of the branches, three reactance elements inseries in the other branch, two of which are tunable to provide a seriesresonant circuit, and an output connection between said two reactanceelements.

17. In an electric signal handling apparatus, a tuned circuit acrosswhich a signal is impressed comprising two parallel branches, acondenser in one of the branches, an inductor and a condenser in seriesin the other branch, and an output connection between the inductor andthe condenser.

18. In an electric signal handling apparatus, a tuned circuit acrosswhich a signal is impressed comprising two parallel branches, areactance element in one of the branches, a pair of reactance elementsin the other branch tunable with each other and with the first namedreactance element to resonance with the signal, and an output connectionbetween the pair of reactance elements.

HARRY W. BECKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,020,297 Buckley Nov. 12, 19352,176,868 Boswau Oct. 24, 1939 2,190,546 Loube Feb. 13, 1940 2,288,487Rosen June 30, 1942 2,346,504 Place Apr. 11, 1944 2,389,949 Becker Nov.27, 1945

